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The value of Delta_fG^@ for formation of Cr_2O_3 is -540 kJ mol^(-1) and that of Al_2O_3 is -827 kJ mol^(-1). Is reduction of Cr_2O_3 possible with Al ? |
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Answer» Solution :The two equations are : (i) `4//3Al(s) + O_2(g)to 2//3Al_2O_3(s),Delta_fG^@ = - 827 kJ MOL^(-1)` (ii) `4//3Cr(s) + O_2(g) to 2//3Cr_2O(s) : Delta_fG^@ = - 540 kJ mol^(-1)` SUBTRACTING Eq. (ii) from Eq. (i), we get `4//3 Al(s) + 2//3 Cr_2O_3(s) to 2//3 Al_2O_3 (s) + 4//3 CR(s): Delta_rG^@ = - 287 kJ mol^(-1)` Since `Delta_rG^@` of the combined redox reaction is negative, therefore, REDUCTION of `Cr_2O_3` by Al is POSSIBLE. |
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